Systems for pressurizing fluids such as liquids include pumps, intensifiers, and other devices for producing pressures. In the majority of cases, valve means are provided whereby fluid can pass into and out of a pressure chamber.
In some cases, two openings and two valves are provided, such as is shown in U.S. Pat. No. 2,807,215. Such a two-valve system involves the use of two separate openings into the pressure chamber and, in many cases, this is not desirable.
Preferably, only a single opening will be provided into the chamber, through which fluid is both admitted and discharged. In order to control the inflow and outflow of fluid, it is known to provide two valves connected to the single opening. One such system is shown in U.S. Pat. No. 3,811,798. In this system, however, the arrangement of the two valves is such that they are located on an axis which is transverse to the axis of the pressure chamber. Consequently, the efficiency of the device as a pressurizing device is significantly reduced. That portion of the transverse valve passage which communicates with the pressure chamber constitutes an unswept volume. The efficiency of this type of pressure device, whether it is a pump or an intensifier, depends to a large extent on reducing the unswept volume to a minimum.
At moderate pressures, e.g. in the range of 1,000 psi, the unswept volume is not a critical factor.
However at high pressures, e.g. in the range of 30,000 psi, major losses in efficiency are experienced due to excessive unswept volume.
In a typical arrangement using two valves on a transverse axis where there is significant unswept volume, efficiency at 1,000 psi might be 97%. However at 30,000 psi efficiency drops to around 68%. This is caused principally by the compressibility of liquids, i.e., water, at these high pressures.
Accordingly for these higher pressure ranges, the industry has adopted a valve arrangement in which the two valves are located on a common axis, along the axis of the pressure chamber. Even this so called "In line" valve arrangement results in significant losses due to unswept volume, due to various design factors.
In particular, valve springs were sometimes used, located within the pressure chamber, which resulted in unswept volume.